Embodiments of the present invention relate to a liquid crystal panel and a manufacturing method thereof, a liquid crystal display device.
A PDLC (polymer dispersed liquid crystal) film is a liquid crystal functional film with excellent performance that is formed by means of dispersing liquid crystals in an organic solid polymer matrix in the form of small droplets in micron scale, and has characteristics of an electrically controlled optical switch under the control of an electric field. Relative to a conventional display device, a liquid crystal display device of a polymer dispersed mode has such merits that it does not need a polarizer and an alignment layer, has a simple manufacturing process, is more easy to be produced into a large-area flexible display, and so on, and has been widely used in the fields of optical modulator, electrically controlled glass, light valve, projection display, electronic book, etc. at present.
When no voltage is applied across the PDLC, an optical axis of each small droplet that is dispersed in the polymer is preferentially oriented according to the lowest energy principle, and thus optical axes of droplets are in the state of a disordered orientation. Because the liquid crystal is a material having strong optical and dielectric anisotropies, and its effective refractivity does not match (or has a larger difference) with the refractivity of a polymer matrix, rays that are incident onto the PDLC may be intensively scattered so as to make the PDLC be shown in an opaque or translucent milky white; when an external electric field is applied across the PDLC, directions of optical axes of liquid crystal droplets are unified to be along the direction of the electric field, the refractivity of the liquid crystal droplets and the refractivity of the polymer achieve a certain degree of match, so that the rays can pass through the matrix, thus PDLC film appears to be transparent or translucent. As such, the PDLC can be used to realize an electrically controlled optical switch by whether or not a voltage is applied to the PDLC.
Currently, the PDLC is manufactured mainly in such a way that a homogeneous system of a polymer and a LC mixture is subjected to phase separation to thereby form dispersed LC droplets in a continuous phase of the polymer. FIG. 1 is a schematic view illustrating the distribution of matter at a certain moment during ultraviolet solidification of a PDLC in prior art, and FIG. 2 is a schematic view illustrating the transmittance of liquid crystal droplets following the ultraviolet solidification of the PDLC as shown in FIG. 1. As shown in FIG. 1 and FIG. 2, in a conventional solidification process of the PDLC, between substrates 71 and 72, the molecular chain of a polymer that is produced by disordered polymerization of polymer 8 tends to wrap on liquid crystal droplets 9, so that the separation between a liquid crystal phase and a polymer phase is difficult. As such, after the PDLC is solidified, the liquid crystal droplets 9 are formed in non-uniform size and distribution, and liquid crystal droplets 9 are oriented differently so that the mutual matching degree between their optical axes is low, thereby leading to a poor transmittance of PDLC to lights L. Moreover, lights on the condition of a wide viewing angle is seriously scattered as well because the matching degree between optical axes of the liquid crystal droplets is too low.
Generally, the dispersion of a liquid crystal phase in a polymer can be improved by means of adding a surfactant into a mixture of liquid crystals and the polymer, etc., so that a PDLC with a wide viewing angle and a high light transmittance is formed after the mixture is solidified and subjected to phase separation. However, the surfactant usually has a small molecular texture, and also has a problem of compatibility with each of polymer and liquid crystal droplets that have larger molecules. Therefore, its effect on improvement of the dispersion is not ideal.